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2-10-3. Characteristics of sine wave control in case of brushless DC motor
Although ordinary three-phase induction motor requires energy to excite the magnetic field of rotor, brushless DC motor
doesn't need it. So, higher efficiency and torque are provided.
This control provides the most efficient waveform corresponding to the rotation times of compressor motor.
The rotation can be set to higher compared to the conventional motor drive system. So, the time in which air conditioner
can be operated with energy saved is longer than conventional models. This can save annual electric consumption.
Compared to square wave control, the torque pulsation is reduced at rotation so that the motor operates more quietly.
Since response and efficiency of motor are enhanced in sine wave control, finer adjustment can be provided.
Rotor
Rotor Position Signal
w In brushless DC motor, permanent magnet is embedded in the rotor. Therefore, it doesn't require energy to excite the rotor
like AC motor does. However, it's necessary to control the frequency of three-phase AC current supplied to the stator
according to the polar direction of magnet embedded in the rotor so as to drive the motor efficiently. Controlling three-phase
AC current frequency also means controlling the timing to switch the polarity of stator. Therefore, the polar direction of rotor
needs to be detected.
2-10-4. Control Method of Rotation Times
Sine wave control makes the current transformers conduct real time detection of the value of the current running into the motor,
locates the rotor position from the detected value, and decides if voltage should be impressed and if frequency should be chan-
ged.
Compared to the conventional control and rotor position detection method, sine wave control can provide finer adjustment of the
voltage of supplied power. The value of the current running into the motor is determined by each motor characteristic.
2-11. OPERATIONAL FREQUENCY CONTROL OF OUTDOOR UNIT
1. Outline
The operational frequency is as following:
First, the target operational frequency is set based on the difference between the room temperature and the set tem-
perature.
Second, the target operational frequency is regulated by discharge temperature protection, high pressure protection,
electric current protection and overload protection and also by the maximum/minimum frequency.
2. Maximum/minimum frequency in each operation mode.
Applied
model
MUZ-GA25VA
MUZ-GA35VA
w The operation frequency in COOL mode is restricted the upper limit frequency after 1 hour as shown below for
dew prevention.
It is rated frequency or less.
Upper limit
frequency
Downloaded from AC-Manual.com Manuals
Permanent magnet is embedded.
Necessary
COOL
Rated
Minimum
Maximum
frequency
frequency
frequency
28
65
28
88
Maximum
frequency
1 hour
DC Motor
HEAT
Minimum
Rated
frequency
frequency
70
48
85
98
45
96
Rated frequency or less
Time
33
AC Motor
Excited by magnetic field of stator
Unnecessary
DRY
Maximum
Minimum
frequency
frequency
105
28
105
28
Maximum
frequency
40
58
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